Filters containing superabsorbent polymers (SAP) have been used in the aviation fueling industry for many years. A major functional requirement is that the filter media absorb undissolved water and remove it from the fuel steam. These types of filters have provided very reliable and robust performance, improving flight safety.
The evaluation of used filters has uncovered performance problems. The SAP present in such filters has been found to have degraded in use, resulting in poorer water absorption. Thus, the removal of water from the transient fuel stream has been compromised.
It has been recognized for years that SAP water absorption is degraded by many water-soluble contaminant compounds. These compounds include alcohols, ethers, other polar organic molecules, and most importantly, inorganic salts. These salt compounds are considered to be rare in normal aviation fuel handling. Based on analysis of used SAP and fuel samples themselves, however, it has been determined that the presence of inorganic salts is much more common than previously thought.
The degradation of SAP in aviation fuel service is now known to be caused by the absorption of inorganic salts into the SAP. This reduces that absorption of water and the subsequent swelling of these polymers.
It is an object of the invention to produce a filter to negate or counteract the deleterious effects of inorganic salts.
Another object of the invention is to produce a filter having the capability of removing inorganic salts from aviation fuels.
Still another object of the invention is to produce a filter which incorporates salt-tolerant SAP materials.
An alternative object of the invention is to produce a filter having the capability of removing salt from the transient fluid by ion exchange.